Smart Responsive Circularly Polarized Luminescence Materials: Design,Construction And Optical Properties

Chirality is one of the widespread phenomena in nature.Exploring the structure and expression of chiral molecule is of great significance for understanding various complex processes in life.Circularly polarized luminescence（CPL）,as one of the characteristics of chiral luminescent materials,mainly refers a phenomenon in that chiral matters emit left-or right-handed circularly polarized light under the excitation of light or electricity.In recent years,chiral optical materials with CPL properties have drawn much interest due to their wide potential applications in optical information encryption storage,bio-encoding and asymmetry polymerization.The construction of responsive circularly polarized luminescent systems plays a vital role in generating smart chiral materials.In this thesis,we focused on the fabrication and improvement of responsive CPL materials.Supramolecular self-assembly,incorporating into chiral liquid crystals and triplet-triplet annihilation photon upconversion were employed,and intelligent circularly polarized luminescent system was developed.The main results and achievements are as follows:（1）Proton triggered CPL switch in a co-assembled gel system composed of an achiral fluorophore and chiral gelator was designed and synthesized.We found that the supramolecular assembly of achiral functionalized molecules with photoinduced electron transfer（PET）properties and chiral gelator can be tuned by solvent.By selecting appropriate solvent,supramolecular assemblies formed by co-assembly can achieve chirality transfer from chiral gels to achiral dyes.Conversely,gels obtained by orthogonal assembly cannot achieve efficient chirality transfer.The co-assembled gel formed chiral nanofibers through chirality transfer,and the protonation of the co-assembled nanofibers in an acidic environment can light up the CPL.However,it was accompanied by the disappearance of the CPL signal when it was exposed to an alkaline environment.An acid-base fumigation driven CPL switch could be realized based on both chirality transfer and reversible protonation of the cogel.（2）CPL active chiral emitter guanidine-substituted 1,8-naphthalimide（R/S-1）with excited-state proton transfer（ESPT）and intramolecular charge transfer（ICT）properties was designed and synthesized,which could emit tunable circularly polarized light through regulating the situation of protonation/deprotonation in aqueous,as well as the solvent polarity.Tunable CPL from blue to yellow under acid/base stimulation was achieved,enabling a single-molecule-white-color circularly polarized light emission,which verified a novel idea to develop tunable CPL materials from a single system in the future.We had successfully achieved single-molecule circularly polarized white light emission in aqueous solution for the first time by precisely adjusting the p H.When the R/S-1 molecule was dissolved in an organic solvent,tunable CPL from blue to yellow was also achieved.This further validated new ideas for developing tunable CPL materials from a single system in the future.In addition,the optical properties of R/S-1 in low-temperature environment were also measured,although lower the temperature will suppress ESPT process,the circular polarization of CPL behavior can be amplified.This provided an efficient way for fabricating higher dissymmetry factor CPL organic nanomaterials.（3）CPL property of R/S-1 in polymer and chiral nematic liquid crystal（N*-LCs）responsive to acid and alkaline were designed and synthesized.We further prepared a composite film containing R/S-1 and polymer.The emission color of the film can be regulated from blue to yellow-green in accordance with the reversible protonation/deprotonation upon external stimuli,using hydrochloric acid and ammonia as encryption and decryption reagents,respectively.In this way,the printed information can be encrypted and decrypted,which showed great potential for information security applications.Additionally,loading the chiral emitters R/S-1 into chiral liquid crystal films,tunable fluorescence and CPL had been demonstrated upon exposing to alkaline atmosphere.Thus,the assembly realized a chiral optical system with stimuli-responsive circularly polarized light emission color and intensity adjustable.Eye-distinguished CPL emission was confirmed assisted by a polarizer.（4）Enantioselective photopolymerization system of upconversion circularly polarized ultraviolet luminescence（UC-CPUVL）in chiral nematic liquid crystal system was designed and synthesized.By integrating sensitized triplet-triplet annihilation upconversion and CPL,both visible-to-UV upconversion emission and UC-CPUVL were obtained in the systems,built of chiral annihilator R-/S-TP and achiral sensitizer 4Cz IPN.The combination showed good CPL performance in diluted solution and a high photon upconversion efficiency.TTA-UC process could further amplify the circular polarization of UC-CPUVL to a larger value.After dispersing this upconversion system into room-temperature achiral nematic liquid crystal,induced chiral nematic liquid crystal could significantly amplify the g_lum value of UC-CPUVL.Further,the UC-CPUVL emission had been used to trigger the enantioselective photopolymerization of diacetylene,resulting in highly controllable and stable chiral polydiacetylene with optical activity.